Wow, that average pH is low compared to my water just over here in the Pittsburgh suburbs. Mine is 8.3. Your water is pretty neutral, mine is alkaline.
Anyways, here's my suggestion: Don't adjust your water this time. Water adjustment is a pretty technical topic and if you want to start doing it, be prepared to experiment. I recently switched to all grain and was quite uptight about water adjustment after reading How to Brew. It had me thinking if I wanted to brew anything other than a copper-to-amber beer, I would have to adjust my water. Contrarily, most of the advice I got here and on other forums pretty much said to go without it until you have everything else dialed in. Furthermore, Palmer has more recently (on Brew Strong) said something like, "The malt wants to become beer. You can do things to help it along, but as long as you're close with your water, temperature, etc, it's going to come out pretty good."
If I were you, I would brew the recipe without adjusting the water, then brew it again with water adjustments. As for how to adjust the water, these nomographs should get you started. But they're just a start. Look into books on brewing water chemistry. I don't own any, but if anyone does, please drop a comment on this answer with titles & links.